Charged Kaon Production Yield Studies with Stretcher

Sergei StriganovFermilab

Future of Kaon Physics at FermilabAugust 21, Fermilab

Introduction

• Target: estimate ratio of low energy charged kaon yields at 120 and 24 GeV/c

• There is no solid theoretical basis to create model of low-energy kaon production in proton-nucleus collisions

• Verify model estimates of low energy charged kaon yield in proton-nucleus interaction at 24 - 120 GeV/c

• Simulate kaon yield from thick target

Experimental data on low energy charged kaon production at small angles in proton-nucleus (p ≥ 24 GeV/c)

Incident momentum (GeV/c)

Secondarymometum(GeV/c)

Partilce Target Experiment Comment

24 4 – 18 K+,K- Be,Al,Cu,Pb Eichten et al

24 1.06, 1.4 K- C,Cu,W Amann et al

28 0.66,0.73 K- Al,Cu,Pt Show et al

67 5 - 40 K+,K- Be,Al,Cu Bozhko et al Normalization!

70 1.5 K+,K- Al,W Barkov et al

158 4.6 K+,K- Pb NA49 trigger

200 0.1-1.79 K+,K- S,Au NA35 central

450 4,8 K+,K- Be,S,Pb NA44 trigger

450 6.75-67.5 K+,K- Be NA56/SPY

We need data near kaon momenta of 500 MeV/c at 120 GeV/c ( 0.00417) 710 MeV/c at 24 GeV/c ( 0.03)

Charged kaon ratio at 24 GeV/c

• K+ /K- ratio at small kaon momentum and angles depends on primary proton energy

and target• Ratio falls as s-.5

between 12 and 70 GeV/c (s is center-of-mass energy)

Charged kaon ratio at 24 GeV/c

24 GeV/c ratio = 2.6 for Be, ratio = 3.2 for Pb

Models• LAQGSM is Los Alamos version

of the Quark-Gluon String Model• LAQGSM is implemented into

MARS code system. It is possible to simulate thick target production.

• All LAQGSM results in this presentation were obtained using MARS-LAQGSM, not with the original LAQGSM!

• MARS default generator is based on approximation of measured inclusive spectra in hadron-proton collisions and nuclear modification factor calculated using additive quark model

• Efremov, Kazarnovsky, Paryev (EKP) developed closed analytical

expressions for inclusive cross section for K+ and K- production in proton-proton and proton-nucleus collisions based on experimental data

• Bonesini, Marchionni, Pietropaolo, Tabarelli proposed parameterization of experimental data measured in pBe interactions at 400-450 GeV/c.

It is supposed that nuclear modification factor does not depend on secondary particle type and incident beam momentum. Radial scaling variable is used, so model could be applied at momentum > 20 GeV/c

Parametrizations and experimental data

Parametrizations and experimental data- II

MARS default generator and experimental dataWe need data near kaon momenta of 500 MeV/c at 120 GeV/c ( 0.00417) 710 MeV/c at 24 GeV/c ( 0.03)

MARS default generator and experimental data-IIWe need data near kaon momenta of 500 MeV/c at 120 GeV/c ( 0.00417) 710 MeV/c at 24 GeV/c ( 0.03)

MARS-LAQGSM generator and experimental data

We need data near kaon momenta of 500 MeV/c at 120 GeV/c ( 0.00417) 710 MeV/c at 24 GeV/c ( 0.03)

MARS-LAQGSM generator and experimental data-II

We need data near kaon momenta of 500 MeV/c at 120 GeV/c ( 0.00417) 710 MeV/c at 24 GeV/c ( 0.03)

From thin to thick target

• Kaon production target is about

0.6 -1 nuclear interaction length• Low energy kaons could be produced

in secondary, tertiary … interactions• K+ with kinetic energies 336-560 MeV

are mostly produced in primary proton interactions and near elastic scattering of low energy positive kaon

• Results obtained using MARS- default and MARS-LAQGSM are similar

• About 30% of low energy positive kaons are produced by secondary neutrons and pions even in short (0.6 nuclear interaction length) target

24 and 120 GeV/c charged meson yield. LAQGSM predictions

120 to 24 GeV/c thick target ratio. LAQGSM predictions

MARS-LAQGSM predicts rise of K+ yield about 3.5 times from 24 to 120 GeV/c. It is not far from about 2.5 rise in experimental data from 24 to 158 GeV/c proton-lead interactions.

MARS-LAQGSM predicts rise of K- yield about 5 times from 24 to 120 GeV/c. It is close to about 5 rise in experimental data from 24 to 158 GeV/c proton-lead interactions.

K+/π+ ratio increases about 15%

from 24 to 120 GeV/c. K-/π- ratio rises about 70% in this energy range

K+ (120 GeV/c) / K+ (24 GeV/c) 490 +- 4% MeV/c / 710 +- 5% MeV/c 1.2 540 +- 4% MeV/c / 710 +- 5% MeV/c 1.8

Conclusion

• Most of experimental data on low energy kaon yield at high proton momentum (> 158 GeV/c) were obtained with different biases. May be it is reason for disagreement between results of NA44 and SPY collaboration. Additional experimental data are needed to clarify situation (MIPP ?).

• Parametric models can not reproduced measurements at heavy nuclei• MARS default generator agrees with data at 24 GeV/c, but

underestimates charged kaon yield at larger energies• MARS-LAQGSM generator underestimates kaon yield from Be target,

but it predictions are closer to data for lead target.• Large fraction of low momentum kaons are produced in secondary

interactions even in short target platinum target

• MARS-LAQGSM thick target simulation predicts about 3.5 rise of low energy positive kaon yield from 24 to 120 GeV/c

BACKUP SLIDES

Normaliztaion of Bozhko et al data

Charged kaon production at 24 GeV/c

E802 data and models

y=0.7 and mT-mp=0.26 GeV ↔ p=0.81 GeV/c and θ=450

Models and data at 12.9 GeV/c

Models and data

• Kapinos model (and original BKP model) can not reproduce data at large x (p/p0 > 0.1) & small angle, and small x &large angles simultaneously (p is kaon and and p0 is proton momentum)

• With Kapinos scale BKP model describes well data at p~1 GeV/c and p0 > 12 GeV/c, with original scale BKP reproduces well high-x and low-angle experimental data

• LAQGSM systematically underestimates low-x measurements

• Both models reproduce well large angle e802 results at 14.6 GeV/c

From thin to thick target

• Simple linear dependence on target thickness is used in Kapinos model

• MARS-LAQGSM simulates kaon production in hadronic shower

• Simplest model – kaon production and absorption:

θ~0 Σin (exp(-Σin x) - exp(-Σout x))/(Σout - Σin)

~ Σinx exp(-(Σin+ Σout )x/2)

θ~1 1-exp(-Σin x)

• Kaon production in secondary interactions is not important at least in 8-12 GeV/c momentum range